Intercellular lipids give a physicochemical barrier effect to the skin. Intercellular lipids mainly include ceramides, fatty acids, cholesterols, cholesterol esters, or the like, and the proportion of ceramides reaches about 40-60%. Ceramides play a very important role in forming a lipid structure and providing a barrier function. Ceramides have characteristics which are difficult to be handled in a cosmetic formulation due to the Wan der Waals attraction between non-polar tails and intermolecular hydrogen bonding occurring in the amino-carbonyl groups and hydroxyl groups of polar head groups. Pseudo-ceramides also have unique thermal behaviors due to their geometrical structures and hydrogen bonding of the head groups, and thus have a difficulty in designing a formulation and controlling a manufacturing process.
Spherical microparticles including polymers have a size and shape controllable depending on preparation methods thereof, and thus have high applicability. For example, there is provided Pickering emulsion which uses spherical microparticles to form stabilized macroemulsion particles. The contact angle (θ) between an aqueous phase and an oil phase varies with hydrophilicity/hydrophobicity of spherical particles. When a contact angle is larger than 90°, O/W emulsion particles are formed. Meanwhile, when a contact angle is smaller than 90°, W/O emulsion particles are formed.
In addition, some attempts have been made to impart amphiphilic property (i.e. both hydrophilic property and hydrophobic property) to spherical microparticles so that novel anisotropic powder may be obtained. This may be exemplified by Janus spherical particles. However, such spherical particles have a limitation in chemical anisotropy due to their morphological limitation. In other words, although the particles are morphologically anisotropic, they may be hydrophobic or hydrophilic as a whole, and thus have limited chemical anisotropy.
Therefore, some attempts have been made to obtain surface active anisotropic powder by controlling a geometrical shape and imparting chemical anisotropy. However, no method for mass production of amphiphilic anisotropic powder has been developed to date, although such amphiphilic anisotropic powder shows high applicability. Moreover, it is difficult to produce amphiphilic anisotropic powder uniformly in a large amount in an industrial scale, leading to a failure in practical application.